In packet-based networks an identifier indicative of the destination of a data packet is typically added to each data packet. The identifier may be globally unique over the entire network (e.g., Ethernet) or locally unique over a portion of the network (e.g., for a specific link such as Multi-Protocol Label Switching (MPLS)). An advantage of globally unique identifiers is elimination of a requirement for a signaling protocol to create a connection prior to information transfers. For locally unique identifiers, since each pair of nodes along the routing path must agree on assignment of an identifier to each transferred frame, a signaling protocol is required.
For unicast communications, globally unique identifiers enable efficient routing of packets through the network (i.e., each endpoint is associated with an identifier which operates as a unique address for the endpoint). This model is used in existing networks (e.g., Ethernet networks and Internet Protocol (IP) networks). In this model, for an identifier size of x bits, at most 2x endpoints may be supported. This model for unicast communications is operationally efficient. Disadvantageously, however, multicast communications may be significantly more complicated. In multicast communications, a multicast tree (including endpoints interested in receiving particular traffic) must generally be formed prior to transmission of the particular traffic.
Furthermore, for multicast communications, since each possible subset of endpoints may form a multicast group, for a network having n endpoints, 2n−n possible multicast groups may be formed in the network. Since n=2x (where x is the number of bits in each identifier), 2x bits are required in order to uniquely identify each possible multicast group. Since, in general, only a subset of possible multicast groups will be utilized, the actual number of multicast group identifiers may be lower (e.g., typically on the order of the number of unicast identifiers). Although an existing approach utilizes an additional bit in the identifier for distinguishing between a unicast identifier and a multicast identifier, this approach still requires a signaling mechanism for maintaining associations between multicast groups and multicast identifiers.